1 files changed, 34 insertions, 2 deletions

diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
index fb0cb2b817a9..7d45c84c69ba 100644
--- a/arch/arm/mach-omap2/timer.c
+++ b/arch/arm/mach-omap2/timer.c
@@ -54,6 +54,7 @@
 
 #include "soc.h"
 #include "common.h"
+#include "control.h"
 #include "powerdomain.h"
 #include "omap-secure.h"
 
@@ -496,7 +497,8 @@ static void __init realtime_counter_init(void)
 	void __iomem *base;
 	static struct clk *sys_clk;
 	unsigned long rate;
-	unsigned int reg, num, den;
+	unsigned int reg;
+	unsigned long long num, den;
 
 	base = ioremap(REALTIME_COUNTER_BASE, SZ_32);
 	if (!base) {
@@ -511,6 +513,35 @@ static void __init realtime_counter_init(void)
 	}
 
 	rate = clk_get_rate(sys_clk);
+
+	if (soc_is_dra7xx()) {
+		/*
+		 * Errata i856 says the 32.768KHz crystal does not start at
+		 * power on, so the CPU falls back to an emulated 32KHz clock
+		 * based on sysclk / 610 instead. This causes the master counter
+		 * frequency to not be 6.144MHz but at sysclk / 610 * 375 / 2
+		 * (OR sysclk * 75 / 244)
+		 *
+		 * This affects at least the DRA7/AM572x 1.0, 1.1 revisions.
+		 * Of course any board built without a populated 32.768KHz
+		 * crystal would also need this fix even if the CPU is fixed
+		 * later.
+		 *
+		 * Either case can be detected by using the two speedselect bits
+		 * If they are not 0, then the 32.768KHz clock driving the
+		 * coarse counter that corrects the fine counter every time it
+		 * ticks is actually rate/610 rather than 32.768KHz and we
+		 * should compensate to avoid the 570ppm (at 20MHz, much worse
+		 * at other rates) too fast system time.
+		 */
+		reg = omap_ctrl_readl(DRA7_CTRL_CORE_BOOTSTRAP);
+		if (reg & DRA7_SPEEDSELECT_MASK) {
+			num = 75;
+			den = 244;
+			goto sysclk1_based;
+		}
+	}
+
 	/* Numerator/denumerator values refer TRM Realtime Counter section */
 	switch (rate) {
 	case 12000000:
@@ -545,6 +576,7 @@ static void __init realtime_counter_init(void)
 		break;
 	}
 
+sysclk1_based:
 	/* Program numerator and denumerator registers */
 	reg = readl_relaxed(base + INCREMENTER_NUMERATOR_OFFSET) &
 			NUMERATOR_DENUMERATOR_MASK;
@@ -556,7 +588,7 @@ static void __init realtime_counter_init(void)
 	reg |= den;
 	writel_relaxed(reg, base + INCREMENTER_DENUMERATOR_RELOAD_OFFSET);
 
-	arch_timer_freq = (rate / den) * num;
+	arch_timer_freq = DIV_ROUND_UP_ULL(rate * num, den);
 	set_cntfreq();
 
 	iounmap(base);